1. Field of Invention
The present invention relates to an explosion power-operated setting tool for driving fastening elements in a structural component and including a housing, a piston guide arranged, at least partially, in the housing and having a guide chamber, a setting piston displaceably arranged in the guide chamber of the piston guide, a resetting device having a resetting member for returning the setting piston in its initial position after completion of a setting process, and a spring for resiliently biasing the resetting member in a direction of its initial position.
2. Description of the Prior Art
Setting Tools of the type described above are driven, e.g., with solid fuels in form of cartridges, which are filled with an explosive powder, or in form of pellets which are formed of a compressed explosive powder. The setting tools includes a housing, a piston guide arranged, at least partially in the housing, and a setting piston displaceably arranged in the piston guide. In these setting tools, the setting piston is driven by combustion gases of the fuel. With the setting piston, fastening elements such as nails, bolts, etc. are driven in constructional components. After completion of each setting process, the setting piston should return into its initial position.
German Publication DE-19749027A1 discloses a hand-held, explosive powder charge-operated setting tool which includes a setting piston resetting device. The resetting of the setting piston is effected with a spring-biased, lever-shaped resetting member which forms part of the resetting device and which pivots relative to the housing in a plane extending in the setting direction. The lever-shaped resetting member projects through a side opening of the piston guide into the interior of the piston guide and cooperates therewith a driving surface of the setting piston facing in the setting direction. The resetting member pivots about a rotational axle supported in the setting tool housing. The biasing spring, which cooperates with the resetting member is supported, on one hand against the housing and, on the other hand, against a stop or rear surface of the lever-shaped resetting member. Upon displacement pivots up to a stop on a damping member and, thereby, the spring becomes preloaded. After the completion of a setting process, the spring is relaxed, providing for pivoting of the resetting member in a direction opposite to the setting direction until the setting piston is returned to its initial position.
The drawback of the known setting tool consists in that the preloading of the spring of the resetting device during the setting process takes place at a high deflection speed, which leads to transient oscillations and a following natural oscillation. These oscillations result in a short service life of the spring.
Accordingly, an object of the present invention is a setting tool of the type described above and in which the foregoing drawback is eliminated, and the resetting device has an improved service life.